I don't know if this will help, but I got this same error when I upgraded to 804.027. I was using a LabEntry and found that this was a case of making sure to use the strict notation verse the shorthand which Lidie's book says is ok
need to do this

 -labelPack=>[-side=> 'left'],
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and not this

 -labelPack, [-side, 'left' ]
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which used to work fine, and in fact some of widgets still let you use the shorthand... but others don't ( you can't use short hand with place )
JamesNC